The present invention relates generally to torque metering apparatus, and more particularly, to improvements in approaches involving sensing of the differential angular displacement of opposite ends of a torsioning shaft section.
Direct measurement of the torsional stress applied to a shaft via conventional strain-gauge technology suffers the significant disadvantage of the elaborate means required to extract the electrical torque signal from the rotating transducers. Slip-rings and brushes commonly used are expensive, deteriorate with age, and are susceptable to noise generated by contamination of the apparatus. Rotating transformer approaches, while eliminating the problems inherent in slip-rings, require considerable and expensive external excitation and detection circuitry to extract the strain-gauge signal, which, itself, often requires additional amplification before use, for example, in driving a panel meter.
Contactless indirect torque measurement means utilizing optical sensing of the angular displacement of opposite ends of torsioning shaft section have previously been devised, and most offer simplicity of construction and consequential low cost as advantages over the conventional direct-measurement approaches above. None of these devices, however, combines all of the features desired in a practical and inexpensive torque transducer. Specifically, it is a primary object of this invention to improve upon devices of the type described in U.S. Pat. Nos. 3,495,452 and 3,596,100 to C. E. Johnson, et al., and R. W. Hollick respectively. These devices utilize the subject optical sensing approach, however, are limited in their application and economy due to inherent necessity to frequently compensate for variations in light source intensity, and, in the one case, elaborate external compensation required for inherent non-linearity.
Therefore, among the objects of the present inventions are the provisions of a torque transducer utilizing differential optical sensing means wherein:
A. an electrical signal output is developed proportional to applied shaft torque with a minimum un-compensated non-linearity, and, PA1 b. said signal output is insensitive to changes in transducer light source intensity due to variations in excitation voltage or aging, PA1 c. while, at the same time, additional desirable performance and construction features are not compromised.
Other and further objects of the present invention will be apparent from the following description and claims and are illustrated in the accompanying drawings which, by way of illustration, show preferred embodiments of the present invention and the principles thereof and what are now considered to be the best modes contemplated for applying these principles. Other embodiments of the invention employing the same or equivalent principles may be used and structural changes may be made as desired by those skilled in the art without departing from the present invention and the purview of the appended claims.